MECHANICAL ENGINEERING Higher

Transcription

1 MECHANICAL ENGINEERING Higher Third edition published December 1999

2 NOTE OF CHANGES TO ARRANGEMENTS THIRD EDITION PUBLISHED ON CD-ROM DECEMBER 1999 COURSE TITLE: Mechanical Engineering (Higher) COURSE NUMBER: C National Course Specification: Course Details: Core skills statements expanded National Unit Specification: All Units: Core skills statements expanded Mechanical Engineering: Higher Course 1

3 National Course Specification MECHANICAL ENGINEERING (HIGHER) COURSE NUMBER C COURSE STRUCTURE This course comprises three mandatory units, as follows: D Dynamics (H) 1 credit (40 hours) D Strength of Materials (H) 1 credit (40 hours) D Thermofluids 1 credit (40 hours) In common with all courses, this course includes 40 hours over and above the 120 hours for the component units. This is for induction, extending the range of learning and teaching approaches, support, consolidation, integration of learning and preparation for external assessment. This time is an important element of the course and advice on its use is included in the course details. RECOMMENDED ENTRY While entry is at the discretion of the centre, candidates would normally be expected to have attained one of the following: Intermediate 2 Structures, together with Mathematics and Physics at Intermediate 1 or above Standard Grade Mathematics with either Standard Grade Technological Studies or Physics at grade 2 or above equivalent or appropriate National units or courses Intermediate 2 Scottish Group Award in a related area. Administrative Information Publication date: December 1999 Source: Scottish Qualifications Authority Version: 03 Scottish Qualifications Authority 1999 This publication may be reproduced in whole or in part for educational purposes provided that no profit is derived from reproduction and that, if reproduced in part, the source is acknowledged. Additional copies of this specification (including unit specifications) can be purchased from the Scottish Qualifications Authority for Note: Unit specifications can be purchased individually for 2.50 (minimum order 5). 2

4 National Course Specification (cont) COURSE Mechanical Engineering (Higher) CORE SKILLS This course gives automatic certification of the following: Complete core skills for the course Numeracy Int 2 Additional core skills components for the course Critical Thinking H Using Number H Additional information about core skills is published in Automatic Certification of Core Skills in National Qualifications (SQA, 1999). Mechanical Engineering: Higher Course 3

5 National Course Specification: course details COURSE Mechanical Engineering (Higher) RATIONALE The products of mechanical engineering innovation surround us. They contribute in some form to virtually every area of human endeavour and without them, society as we know it could not function. The range of applications of mechanical engineering is enormous, varying in scale and precision from the micro-miniature to immense structures in the form of bridges, supertankers, oil platforms and tower blocks. Mechanical engineering s contribution to economic growth and the development of society has been and still is immense. Where would society be without electricity generating stations, oil refineries, modern transportation systems? Modern motor vehicles, high-speed trains and fast, quiet, reliable passenger aircraft are obvious examples of the way in which mechanical engineering has played a major part in sophisticated modern products which have become essential to our everyday lives. Perhaps less obvious but equally important to individuals and to society is the role which mechanical engineering has played in the development of modern medical equipment, from allbody scanners to artificial heart valves. Many of the complex peripheral devices which are an essential feature of modern information technology systems rely heavily on advanced mechanical engineering designs. This course provides the opportunity for individuals to develop the skills and knowledge to help them understand mechanical engineering concepts which underpin so many exciting developments. The course is intended to provide the candidate with the knowledge and understanding of a broad section of mechanical engineering principles and applications. It will establish important fundamentals for those interested in a career in a variety of mechanical engineering disciplines. The breadth of study makes it a worthwhile contributor to general education and the advancement of technological capability. The aim of the course is to bring a level of knowledge and understanding to candidates who wish to seek employment as technician engineers or entry to study at a higher level. Successful completion of this course will indicate that a candidate has mastered the fundamental concepts required for quantitative analysis in major areas of technological capability. The components of the course when successfully completed will allow candidates to apply the principles and laws which relate to: changes in linear and angular motion effects of static loads causing bending and twisting, including designing for these conditions gas laws and the use of properties of vapours to analyse and solve problems associated with simple steady flow energy applications The knowledge, understanding, skills, attitudes and confidence developed will promote ways of thinking which help to draw together aesthetic, economic and environmental factors with ergonomic, technical and scientific principles. This knowledge will also improve the candidate s ability to relate technological capability to everyday situations. The course will also allow practice of a number of core skills (Critical Thinking and Using Number) within a technological context. Mechanical Engineering: Higher Course 4

6 National Course Specification: course details (cont) COURSE Mechanical Engineering (Higher) COURSE CONTENT All of the course content will be subject to sampling in the external assessment. The separate units reflect the three main strands of mechanical engineering theory and principles. Once competence has been reached in using these techniques in an individual way, the full process of mechanical engineering can begin where the candidate learns to analyse a situation and develop an engineering solution. A full investigation of the system and its parameters leads to the ordering of relevant information to allow informed decisions to be taken on the size of the system, its power requirements, material selection, safety considerations, quality and performance requirements. Candidates successfully completing the course, as distinct from achieving the individual units, should benefit from being skilled in a holistic approach to the analysis of a situation. This will require a mechanical engineering solution to be developed from various possibilities which have been considered and compared. The optimum solution would then be progressed to final mechanisms, components, materials and dimensions. This approach will require candidates to: integrate aspects of the course content apply knowledge and skills in a wide range of contexts demonstrate a familiarity of course content beyond that indicated in the unit specifications apply knowledge and skills in a more complex way Some examples of techniques used to help candidates achieve these additional demands, follow. The force and turning effects caused by fluids on submerged surfaces such as valves or gates are studied in the Thermofluids unit. Such forces are often resisted or overcome by mechanical devices such as levers or torsionally loaded members which are studied in the Strength of Materials unit. The course ensures that integration of the content of units takes place and confirms the interrelationship of engineering solutions. The range of contexts can be widened in a large number of ways. For example, the analysis of temperature effects endured by components in thermodynamic devices may well lead to the study of residual stress situations. This extends the context in which loading is usually considered to be caused by force or weight application. Some of the additional 40 hours could be used to analyse a range of carefully chosen engineering applications to widen the range of the candidate s experience. Application of knowledge and skill in more complex situations can be approached in several ways. Analysing a range of applications widens experience, and some scenarios may include consideration of a greater number of variables or the use of specialist software to deduce parameters. The syllabus to be covered in relation to the component units can be attempted either concurrently or sequentially. The added value of the course award would be achieved by applying the principles and techniques mastered in the separate units to situations where some dynamic, strength of material and Mechanical Engineering: Higher Course 5

7 National Course Specification: course details (cont) COURSE Mechanical Engineering (Higher) thermofluid factors are present. Decisions reached from separate analyses require to be synthesised in order to achieve a solution allowing for all relevant factors. The techniques required to achieve this holistic approach can be developed as part of the additional 40 hours making up the course. SUMMARY OF COURSE CONTENT Dynamics (H) Solution of problems related to systems which have elements moving linearly or angularly in order to calculate force, torque, work and power quantities associated with systems of this type. Solution of problems using Newton s Second Law as applied to linear and angular motion. Condition of centripetal acceleration, including the calculation of centripetal force. Candidates should learn that prime movers such as turbines use working fluids such as gas or vapour to cause the dynamic effects being analysed. The size and shape of structural members and components such as shafts are deduced using the techniques developed in the Strength of Materials unit. Mechanical Engineering: Higher Course 6

8 National Course Specification: course details (cont) COURSE Mechanical Engineering (Higher) CONTENT STATEMENTS Dynamics (H) The content statements given in the left-hand column of the table below describe in detail what the candidate should be able to do in demonstrating knowledge and understanding associated with dynamics. The right-hand column gives suggested contexts, applications, illustrations and activities associated with the content statement. KNOWLEDGE AND UNDERSTANDING Linear and angular motion 1 Velocity vs. time diagrams, leading to the use of equations of motion. CONTEXTS, APPLICATIONS, ILLUSTRATIONS AND ACTIVITIES Application to both linear and angular systems. To calculate both displacement and acceleration quantities. The relationship between the linear and angular parameters. 2 Apply Newton s second law. 3 Combined problems. Work and power transfer 1 Definitions of quantities. 2 Calculate work and power quantities. Energy balances 1 Define different forms of energy. 2 The law of conservation of energy. Centripetal acceleration 1 Describe the parameters of circular motion. 2 Solving problems. 3 Centripetal force experiment. To determine the relationship between force, mass and acceleration/torque, inertia and angular acceleration. Solution of dynamic problems involving one linear and one angular component. Quantifying units as joules, joules per second, watts. Pick up examples from the force/torque calculations and extend them to work and power. Kinetic and potential. Energy balances can be used as an alternative method of solving the problems above. Centripetal acceleration and force. Relate the theoretical analysis to practical situations such as vehicles, centrifugal clutch and simple balancing requirements. A simple experiment to verify the theory by balancing linear and angular forces and then comparing the theoretical and practical results. Mechanical Engineering: Higher Course 7

9 National Course Specification: course details (cont) COURSE Mechanical Engineering (Higher) SUMMARY OF COURSE CONTENT Strength of Materials (H) Design requirements for statically loaded components and structures subjected to temperature change, bending and twisting will be arrived at by analysis of the loading conditions. Further factors relating to determination of appropriate design require maximum stress to be calculated, and the necessary shape and size of support members to be deduced so that the components or structure function safely. Loaded structures and devices under combined loading effects, such as direct and bending stress, will also be analysed. Reference should be made during presentation to the dynamic effects on moving systems causing extra forces to be experienced by the structural components, and also to the fact that if the system is part of a thermodynamic device, it will be influenced by effects such as considerable temperature change. Mechanical Engineering: Higher Course 8

10 National Course Specification: course details (cont) COURSE Mechanical Engineering (Higher) CONTENT STATEMENTS Strength of Materials (H) The content statements given in the left-hand column of the table below describe in detail what the candidate should be able to do in demonstrating knowledge and understanding associated with strength of materials. The right-hand column gives suggested contexts, applications, illustrations and activities associated with the content statement. KNOWLEDGE AND UNDERSTANDING Simply supported beams and cantilevers 1 Calculation of reactions. 2 Construction of bending moment, shear force and thrust diagrams. Simple bending theory 1 Familiarisation with the simple bending equation. 2 Solve problems associated with the simple bending theory. The torsion equation 1 Familiarisation with the simple torsion equation. 2 Solve problems associated with the simple torsion theory. Design components 1 Extracting material properties from databases. 2 Deduce design stresses. 3 Analyse loading conditions. CONTEXTS, APPLICATIONS, ILLUSTRATIONS AND ACTIVITIES By taking moments or using force balances. Diagrams are to include point loads, uniformly distributed loads, turning points, zero shear, points of contraflecture. All parameters are to be identified by words and symbols, correct units for all values. Calculation of the second moment of area/section modulus for simple cross-sections. These should include the determination of the stress distribution across the cross-section of the beam. All parameters are to be identified by words and symbols, correct units for all values. Calculation of the polar second moment of area for simple cross-sections restricted to solid and hollow circular shafts. These should include the determination of the stress distribution across the cross-section of the shaft. Minimum of six materials to be considered. The properties should include elastic limit or proof stress, ultimate strength, moduli of elasticity and rigidity. Deductions should take into account loading considerations, environmental effects, cyclic effects and shearing situations. To include any two combined effects. Mechanical Engineering: Higher Course 9

11 National Course Specification: course details (cont) COURSE Mechanical Engineering (Higher) SUMMARY OF COURSE CONTENT Thermofluids (H) The movement of working fluids and corresponding changes in fluid properties will be analysed for flow through thermodynamic equipment such as boilers, heat exchangers, turbines, compressors and the connecting circuits. This requires candidates to calculate energy changes in the fluid, and transfer of work and heat quantities to and from the system. The behaviour of fluids at rest is investigated to permit candidates to analyse applications such as manometers and force on submerged areas, and allow problem-solving in these contexts. Reference should be made in the unit to the fact that the purpose of many thermodynamic devices is to transfer heat and work from the system. As a consequence of these processes, dynamic effects occur to some of the structural members. This causes a clear path of interactive developments between the behaviour of the working fluid, the dynamic effects on the system components, and the necessary size and shape for the system to perform its function effectively and safely. During the additional 40 hours study time associated with the course, several examples of systems involving dynamic effects caused by thermofluids should be observed and analysed. This could be done progressively, leading to further quantitative analysis of these and other systems, involving subject matter from any two of the three units which make up the course. The strength of the course award as opposed to achievement of the individual units is in the ability fostered in the candidate to look at a system as a whole, and analyse the thermofluid, dynamic and structural requirements in order to decide material and dimensional requirements. The candidate will develop powers of logical analysis, the ability to decide which parameters in a complex situation are important, and how these effects impinge on other related factors, and so come to a preferred solution. In order not to overburden the candidate with complexity, particular applications should only sample across the outcomes of any two units. CONTENT STATEMENTS Thermofluids (H) The content statements given in the left-hand column of the following table describe in detail what the candidate should be able to do in demonstrating knowledge and understanding associated with thermofluids. The right-hand column gives suggested contexts, applications, illustrations and activities associated with the content statement. Mechanical Engineering: Higher Course 10

12 National Course Specification: course details (cont) COURSE Mechanical Engineering (Higher) CONTENT STATEMENTS Thermofluids (H) KNOWLEDGE AND UNDERSTANDING The Gas Laws 1 Describe the individual laws. 2 Use the combined gas law. 3 Solve problems involving perfect gases. 4 Solve practical problems. 5 Practical work. Properties of vapours 1 Extract data for thermodynamic property tables. CONTEXTS, APPLICATIONS, ILLUSTRATIONS AND ACTIVITIES Boyle s law or Charles s law could be used as examples. PV = Constant, PV = mrt T To include the calculation of properties. Internal combustion engines, gas turbines and nozzles. Where possible, practical demonstrations should be used. Fluids should be limited to water and refrigerants. Properties are to include saturation temperature and pressure, internal energy, enthalpy specific volume. In undercooled liquid, saturated liquid, wet vapour, saturated vapour and super heater vapour conditions. 2 Interpolation of values. 3 Solve problems using data from tables. Steady flow energy equation (SFEE) 1 Input/Output process approach is used to describe common thermodynamic process. 2 Solve problems using SFEE. 3 Applications of the SFEE to analyse practical situations. Restricted to enthalpy, internal energy and specific volume. Problems should include a change of phase. Calculation of dryness fraction and degree of superheat. Problems should be broken down to simplified Input/Output diagrams: for example boiler, heat exchanger or turbine. Starting with problems that eliminate many of the energy terms and increasing the difficulty to a maximum of three subsystems. Analyse a practical situation using SFEE. Mechanical Engineering: Higher Course 11

13 National Course Specification: course details (cont) COURSE Mechanical Engineering (Higher) CONTENT STATEMENTS Thermofluids (H) (cont) KNOWLEDGE AND UNDERSTANDING Flow through pipes 1 Derive Bernoulli s equation from the SFEE. CONTEXTS, APPLICATIONS, ILLUSTRATIONS AND ACTIVITIES Eliminate irrelevant terms and replace specific volume with density. 2 Mass continuity. 3 Solve problems using Bernoulli s equation. Static fluid behaviour 1 Manometry. To include inclined pipe, convergent and divergent pipes, venturimeter, restricted to incompressible flow. Piezometer tube, U-tube manometers only. 2 Convert height differences to flow. 3 Relate pressure on submerged plates to depths. Calculation of thrust on submerged areas and position of centre of pressure on submerged and partially submerged plates. Restricted to pressure on one side only, and rectangular and round plates only. Mechanical Engineering: Higher Course 12

14 National Course Specification: course details (cont) COURSE Mechanical Engineering (Higher) ASSESSMENT To gain the award of the course, the candidate must pass all the unit assessments as well as the external assessment. External assessment will provide the basis for grading attainment in the course award. When the units are taken as component parts of a course, candidates will have the opportunity to achieve a level beyond that required to attain each of the unit outcomes. This attainment may, where appropriate, be recorded and used to contribute towards course estimates, and to provide evidence for appeals. Additional details are provided, where appropriate, with the exemplar assessment materials. Further information on the key principles of assessment is provided in the paper Assessment (HSDU, 1996) and in Managing Assessment (HSDU, 1998). DETAILS OF THE INSTRUMENTS FOR EXTERNAL ASSESSMENT The external assessment will comprise a written examination paper. The time allocation for the question paper will be 3 hours. The paper will be worth 100 marks and will be in three parts as follows: Section A 50 marks Ten short answer questions will be set. The questions will sample widely across the content of the course. They will assess knowledge and understanding across the component units of the course, in extended and less familiar contexts. Candidates should attempt all questions from this section. Section B 30 marks Three extended answer questions will be set. The questions will assess the candidate s ability to analyse a range of structured problems. Candidates should attempt two questions from this section. Section C 20 marks Two extended answer questions will be set. The questions will assess the candidate s ability to tackle more complex problems and to integrate knowledge from different subject areas in the course. The candidate should attempt one question from this section. The candidate who successfully completes the course assessment should: demonstrate the ability to integrate knowledge, understanding, decision-making and numerical skills acquired in component units and practised in an integrated context retain knowledge and skills levels over the whole length of the course apply knowledge and skills in less familiar contexts apply knowledge and skills in more complex contexts select necessary data as appropriate from information provided Mechanical Engineering: Higher Course 13

15 National Course Specification: course details (cont) COURSE Mechanical Engineering (Higher) GRADE DESCRIPTIONS The descriptions below are of expected performances at grade C and at grade A. they are intended to assist candidates, teachers, lecturers and users of the certificate and to help establish standards when question papers are being set. The grade of the award will be based on the total score obtained in the examination. For performance at grade C, candidates should be able to: Use consistently the knowledge, understanding and skills in the component units of the course. For example in Outcome 4 of the Dynamics unit, the experimental report on centripetal motion would contain a tabular comparison between the actual and theoretical centripetal force at a range of speeds, with the conclusion indicating a broad general correlation with a limited analysis of the variables. Apply the knowledge and understanding gained in the component units correctly to the solution of structured problems in a limited range of contexts. For example in Outcome 2 of the Strength of Materials unit, when using the Simple Bending Equation the correctly related parts of the equation are selected and the values are taken directly from the problem, entered in the equation in the appropriate units and the problem solved. Demonstrate ability to integrate the knowledge, understanding and skills acquired throughout the component units. For example in Outcome 5 of the Thermofluids unit, when solving problems concerning submerged areas, calculated requirements would be restricted to the fluid force and position on the submerged area. For performance at grade A, candidates should be able to: Use the knowledge, understanding and skills acquired in the component units of the course consistently and effectively. For example, in Outcome 4 of the Dynamics unit, the experimental report on centripetal motion would contain a tabular and graphical comparison of the actual and theoretical centripetal force over a relevant range of speeds. The conclusion should indicate quantified sources of errors, possible experimental improvements and a clear consideration of the degree of success achieved during the performance of the experiment. Apply the knowledge and understanding gained in the component units correctly to the solution of unstructured extended problems in more complex contexts. For example, in Outcome 2 of the Strength of Materials unit, when using the Simple Bending Equation the correctly related parts of the equation are selected and the values of up to three of the variables calculated or deduced from the information given in the problem, entered in the equation in the appropriate units and the problem solved. Demonstrate considerable ability to integrate the knowledge, understanding and skills acquired through the component units. For example, in Outcome 5 of the Thermofluids unit, when solving problems concerning submerged areas, calculated requirements would be extended beyond the fluid force and its position on the submerged area to include the application of the principles from the Strength of Materials unit i.e. to calculate other parameters such as a hinge reaction on the submerged area and then appropriate dimensions for the hinge pin. Mechanical Engineering: Higher Course 14

16 National Course Specification: course details (cont) COURSE Mechanical Engineering (Higher) APPROACHES TO LEARNING AND TEACHING Although the course is essentially theoretical in nature, an understanding of practical procedures and of the engineering components and structures which make up the many important systems essential to our civilised way of life, should be studied at every opportunity. Planned visits, possibly to a power station, manufacturing plant or a processing plant such as an oil refinery, video presentations and manufacturers educational materials all have important contributions to make. Case studies of how engineering problems have been solved in the recent past would be a useful resource to focus candidate interest and promote understanding of real world problems and solutions. The additional 40 hours could be used to investigate a range of simplified real engineering systems which depend on aspects of thermofluids, dynamics and strength of materials for their design or operation. Applications should sample across units and require a balance of learning and experience. Numerical analysis should be developed using a series of case studies or coursework of increasing complexity to enable the candidate to draw on the skills acquired in the separate outcomes and units. Group tutorials, practical demonstrations and computer software should all be used where appropriate. In advance of the external assessment, candidates should be given some experience of the type of challenge involved so that they are not surprised by the format and duration. SPECIAL NEEDS This course specification is intended to ensure that there are no artificial barriers to learning or assessment. Special needs of individual candidates should be taken into account when planning learning experiences, selecting assessment instruments or considering alternative outcomes for units. For information on these, please refer to the SQA document Guidance on Special Assessment and Certification Arrangements for Candidates with Special Needs/Candidates whose First Language is not English (SQA, 1998). SUBJECT GUIDES A Subject Guide to accompany the Arrangements documents has been produced by the Higher Still Development Unit (HSDU) in partnership with the Scottish Further Education Unit (SFEU) and Scottish Consultative Council on the Curriculum (SCCC). The Guide provides further advice and information about: support materials for each course learning and teaching approaches in addition to the information provided in the Arrangements document assessment ensuring appropriate access for candidates with special educational needs. The Subject Guide is intended to support the information contained in the Arrangements document. The SQA Arrangements documents contain the standards against which candidates are assessed. Mechanical Engineering: Higher Course 15

17 National Unit Specification: general information UNIT Dynamics (Higher) NUMBER D COURSE Mechanical Engineering (Higher) SUMMARY The unit focuses on applying engineering principles and laws to the analysis of situations involving changes in linear and angular motion. This unit would be useful to candidates who require to develop competence in the application of engineering science principles to dynamic systems. Much of the content is directly useful over a wide range of applications. OUTCOMES 1 Solve problems using Newton s Second Law applied to linear and angular motion. 2 Apply work and power transfer theory to linear and angular systems. 3 Analyse the kinetics of motion using an energy balance approach. 4 Analyse uniform circular motion force systems. RECOMMENDED ENTRY While entry is at the discretion of the centre, candidates would normally be expected to have attained one of the following: Intermediate 2 Structures, together with Mathematics and Physics at Intermediate 1 or above Standard Grade Mathematics with either Standard Grade Technological Studies or Physics at grade 2 or above equivalent or appropriate National units Intermediate 2 Scottish Group Award in a related area. Administrative Information Superclass: RC Publication date: December 1999 Source: Scottish Qualifications Authority Version: 03 Scottish Qualifications Authority 1999 This publication may be reproduced in whole or in part for educational purposes provided that no profit is derived from reproduction and that, if reproduced in part, the source is acknowledged. Additional copies of this unit specification can be purchased from the Scottish Qualifications Authority. The cost for each unit specification is 2.50 (minimum order 5). 16

18 National Unit Specification: general information (cont) UNIT Dynamics (Higher) CREDIT VALUE 1 credit at Higher. CORE SKILLS This unit gives automatic certification of the following: Complete core skills for the unit None Core skills components for the unit Critical Thinking H Using Number H Additional information about core skills is published in Automatic Certification of Core Skills in National Qualifications (SQA, 1999). Mechanical Engineering: Unit Specification Dynamics (H) 17

19 National Unit Specification: statement of standards UNIT Dynamics (Higher) Acceptable performance in this unit will be the satisfactory achievement of the standards set out in this part of the unit specification. All sections of the statement of standards are mandatory and cannot be altered without reference to the Scottish Qualifications Authority. OUTCOME 1 Solve problems using Newton s Second Law applied to linear and angular motion. Performance criteria (a) The elements of motion are accurately defined in accordance with established theory. (b) The interrelationships between the elements of motion are analysed in accordance with established theory. (c) Problems relating to systems affected by uniform acceleration are solved correctly. Note on range for the outcome Motion: linear, angular, combined (limited to one linear and one angular influence). Elements: displacement, velocity, acceleration, time, accelerating force, accelerating torque. Evidence requirements Written and/or oral evidence that the candidate can solve problems using Newton s Second Law as described in the PCs for one simple system with one angular and one linear component of motion. OUTCOME 2 Apply work and power transfer theory to linear and angular systems. Performance criteria (a) Work and power quantities are defined correctly in accordance with established theory. (b) Work and power calculations are performed correctly. (c) Problems related to systems affected by constant and variable applied forces are solved accurately. Note on range for the outcome Systems: linear, angular, combined (limited to one linear and one angular influence). Evidence requirements Written and/or oral evidence that the candidate can apply work and power transfer theory to a simple system containing both linear and angular motion as described in PCs (a) to (c). Mechanical Engineering: Unit Specification Dynamics (H) 18

20 National Unit Specification: statement of standards (cont) UNIT Dynamics (Higher) OUTCOME 3 Analyse the kinetics of motion using an energy balance approach. Performance criteria (a) The influences affecting kinetic energy are defined correctly in accordance with established theory. (b) Energy balance principles are applied to motion systems correctly. (c) Problems relating to systems affected by uniform acceleration are solved accurately. Note on range for the outcome Systems: linear, angular, combined (limited to one linear and one angular influence). Forms of energy: potential, kinetic. Evidence requirements Written and/or oral evidence that the candidate can apply energy balance principles as described in PCs (a) to (c) across all classes in the range. OUTCOME 4 Analyse uniform circular motion force systems. Performance criteria (a) Centripetal acceleration is defined correctly in terms of a requirement for circular motion in accordance with established theory. (b) An experiment to verify the theory of centripetal acceleration is performed satisfactorily. (c) The effect of centripetal acceleration on mechanisms is qualitatively described correctly. Note on range for the outcome Mechanisms: vehicle movement, centrifugal clutch, simple balancing requirements. Evidence requirements Written and/or oral evidence that the candidate can describe uniform circular motion force systems as described in PCs (a) and (c) across all classes of the range, along with written evidence that the candidate has successfully completed the experiment as described in PC (b). Mechanical Engineering: Unit Specification Dynamics (H) 19

21 National Unit Specification: support notes UNIT Dynamics (Higher) This part of the unit specification is offered as guidance. The support notes are not mandatory. It is recommended that you refer to the SQA Arrangements document for Higher Mechanical Engineering before delivering this unit. While the exact time allocated to this unit is at the discretion of the centre, the notional design length is 40 hours. On successful completion of the unit a candidate will be able to solve problems related to systems which have elements moving linearly or angularly. He or she will also be able to calculate force, torque, work and power quantities associated with systems of this type and to analyse systems affected by centripetal acceleration and its related factors. The content of this unit would be directly beneficial for those intending to proceed to a degree or HNC/D course in a range of engineering and related disciplines. GUIDANCE ON CONTENT AND CONTEXT FOR THIS UNIT The application of principles should be supplemented by practical demonstration. Computer software should be made available where appropriate. A graded tutorial system reflecting a wide range of vocational interests would be appropriate for all outcomes. An integrated presentation is possible and this would be reflected by integrated assessment instruments. A simple presentation, demonstration and discussion of motion using either a velocity/time diagram approach or the equations of motion can be combined with application of Newton s Second Law to allow the candidate to become familiar with the terminology and overall parameters involved. Various linear and angular systems can then be analysed and calculations attempted relating force/torque to acceleration. Once single element systems have been mastered, combined linear-angular systems can be introduced and supported by tutorial examples. Work and power calculations can now be introduced and included in previously completed analysis and calculations. Some revision of energy forms and calculations, followed by application of the principle of energy balance, can then be applied to the same systems used in Outcomes 1 and 2, as an alternative method of solution perhaps initially limited to linear systems. Angular systems can then be approached and a more comprehensive understanding of polar movement of inertia attempted, followed by analysis and application to combined systems. Either experimental or theoretical approaches to the dynamics of a single mass rotating in a horizontal circular path can be used to deduce the centripetal acceleration/force necessary to achieve this type of motion. Analysis and calculations on a range of applications can now be completed individually and in small groups. The experimental nature of this type of analysis may be used as a vehicle to stimulate candidate interest in investigation, ordering and analysing results and reaching logical conclusions. This approach would be good preparation for future study. Mechanical Engineering: Unit Specification Dynamics (H) 20

22 National Unit Specification: support notes (cont) UNIT Dynamics (Higher) GUIDANCE ON LEARNING AND TEACHING APPROACHES FOR THIS UNIT Although the unit is essentially theoretical in nature, an understanding of practical procedures and of the engineering components and structures which make up the many important systems essential to our civilised way of life should be studied at every opportunity. Planned visits, possibly to a power station, manufacturing plant or a processing plant such as an oil refinery, video presentations and manufacturers educational materials all have important contributions to make. Case studies of how engineering problems have been resolved in the recent past would be a useful resource to focus candidate s interest and promote understanding of real world problems and solutions. Numerical analysis should be developed using a series of case studies or coursework of increasing complexity to enable the candidate to draw on the skills acquired in the separate outcomes and units. Group tutorials, practical demonstrations and computer software should all be used where appropriate. The content statements given in the left-hand column of the following table describe in detail what the candidate should be able to do in demonstrating knowledge and understanding associated with dynamics. The right-hand column gives suggested contexts, applications, illustrations and activities associated with the content statement. Mechanical Engineering: Unit Specification Dynamics (H) 21

23 National Unit Specification: support notes (cont) UNIT Dynamics (Higher) KNOWLEDGE AND UNDERSTANDING Linear and angular motion 1 Velocity vs. time diagrams, leading to the use of equations of motion. CONTEXTS, APPLICATIONS, ILLUSTRATIONS AND ACTIVITIES Application to both linear and angular systems. To calculate both displacement and acceleration quantities. The relationship between the linear and angular parameters. 2 Apply Newton s second law. 3 Combined problems. Work and power transfer 1 Definitions of quantities. 2 Calculate work and power quantities. Energy balances 1 Define different forms of energy. 2 The law of conservation of energy. Centripetal acceleration 1 Describe the parameters of circular motion. 2 Solving problems. 3 Centripetal force experiment. To determine the relationship between force, mass and acceleration/torque inertia and angular acceleration. Solution of dynamic problems involving one linear and one angular component. Quantifying units as joules, joules per second, watts. Pick up examples from the force/torque calculations and extend them to work and power. Kinetic and potential. Energy balances can be used as an alternative method of solving the problems above. Centripetal acceleration and force. Relate the theoretical analysis to practical situations such as vehicles, centrifugal clutch and simple balancing requirements. A simple experiment to verify the theory by balancing linear and angular forces and then comparing the theoretical and practical results. Mechanical Engineering: Unit Specification Dynamics (H) 22

24 National Unit Specification: support notes (cont) UNIT Dynamics (Higher) GUIDANCE ON APPROACHES TO ASSESSMENT FOR THIS UNIT Outcome 1 An appropriate instrument of assessment could use prepared data for a system of motion containing one angular and one linear component of motion. The data could be applied either to different masses or to the same mass. A structured question would be appropriate, asking the candidate to determine perhaps three parameters of the system before calculating the required applied force/torque necessary to operate the system. Outcomes 2 and 3 Further information could be supplied to the candidate relating to the same system used for Outcome 1. Alternatively, data could be given for another system along with other structured questions requiring determination of three parameters. In much the same way an appropriate instrument of assessment might elicit an energy balance for a system of two elements. This might involve perhaps four terms in an angular energy balance where one parameter of one term is to be calculated. An appropriate instrument of assessment would elicit calculation of power requirements at a particular instant and the average power requirements where a variable force/torque is applied. Outcome 4 A standard apparatus can be used for centrifugal force experiments. Alternatively, a simple device could be made up where the centripetal force exerted on a rotating mass can be measured. The candidate would be presented with this hardware and required to prove that the centripetal force is directly proportional to the mass, radius of the circular motion and the square of the angular velocity. The candidate would then be asked to develop the experimental procedure, conduct the experiment, collect tabulate and analyse the results, and reach valid, logical, supportable conclusions. The report showing that all these factors had been successfully processed would form an appropriate assessment instrument. Short answer questions, possibly based on diagrams of systems, could be used for PC (c) of Outcome 4. It would be possible to use the same motion system for Outcomes 1 to 3, with graded questions covering each outcome. It would also be possible to use an element of this same system to cover Outcome 4 but this would be an unnecessary complication. Overall, however, a balance should be sought between breadth of candidate experience and assessment efficiency. SPECIAL NEEDS This unit specification is intended to ensure that there are no artificial barriers to learning or assessment. Special needs of individual candidates should be taken into account when planning learning experiences, selecting assessment instruments or considering alternative outcomes for units. For information on these, please refer to the SQA document Guidance on Special Assessment and Certification Arrangements for Candidates with Special Needs/Candidates whose First Language is not English (SQA, 1998). Mechanical Engineering: Unit Specification Dynamics (H) 23

25 National Unit Specification: general information UNIT Strength of Materials (Higher) NUMBER D COURSE Mechanical Engineering (Higher) SUMMARY This unit focuses on applying engineering principles to the analysis of situations involving static loads on materials. This unit would be useful to candidates who require to apply engineering science principles to systems under static loading conditions. Much of the content is directly useful over a wide range of applications. OUTCOMES 1 Determine the shear forces and bending moments for simply supported beams and cantilevers. 2 Apply the simple bending theory to idealised beams and cantilevers. 3 Apply the simple torsion equation to shafts of circular cross-section. 4 Design simple components to a given specification. RECOMMENDED ENTRY While entry is at the discretion of the centre, candidates would normally be expected to have attained one of the following: Intermediate 2 Structures, together with Mathematics and Physics at Intermediate 1 or above Standard Grade Mathematics with either Standard Grade Technological Studies or Physics at grade 2 or above equivalent or appropriate National units Intermediate 2 Scottish Group Award in a related area. CREDIT VALUE 1 credit at Higher. Administrative Information Superclass: RC Publication date: December 1999 Source: Version: 03 Scottish Qualifications Authority Scottish Qualifications Authority 1999 This publication may be reproduced in whole or in part for educational purposes provided that no profit is derived from reproduction and that, if reproduced in part, the source is acknowledged. Additional copies of this unit specification can be purchased from the Scottish Qualifications Authority. The cost for each unit specification is 2.50 (minimum order 5). 24

26 National Unit Specification: statement of standards UNIT Strength of Materials (Higher) CORE SKILLS This unit gives automatic certification of the following: Complete core skills for the unit None Additional core skills components for the unit Critical Thinking Int 2 Using Number H Additional information about core skills is published in Automatic Certification of Core Skills in National Qualifications (SQA, 1999). Mechanical Engineering: Unit Specification Strength of Materials (H) 25

27 National Unit Specification: statement of standards UNIT Strength of Materials (Higher) Acceptable performance in this unit will be the satisfactory achievement of the standards set out in this part of the unit specification. All sections of the statement of standards are mandatory and cannot be altered without reference to the Scottish Qualifications Authority. OUTCOME 1 Determine the shear forces and bending moments for simply supported beams and cantilevers. Performance criteria (a) The extent to which beams and cantilevers are statistically determinate is established correctly by calculating reactions. (b) Loading diagrams for beams and cantilevers are drawn correctly. (c) The position of significant values of loading for beams and cantilevers are determined accurately in terms of their application. Note on range for the outcome Reactions: pin, frictionless roller, encastered (cantilever only). Loading diagrams: shear force, bending moment, thrust. Significant values: zero shear/maximum bending, contraflexture. Evidence requirements Written and/or oral and graphical evidence which satisfies PCs (a) to (c) and the range as applied to one loaded beam and one loaded cantilever. OUTCOME 2 Apply the simple bending theory to idealised beams and cantilevers. Performance criteria (a) Each parameter, term and relationship of the simple bending theory is identified consistently with established theory. (b) Parameters associated with second moment of area are determined from charts and calculations consistent with established theory. (c) Loaded beams and cantilevers are analysed correctly in applying the simple bending theory. (d) Problems related to application of the simple bending theory to beams and cantilevers are solved correctly. Note on range for the outcome Parameters: bending moment, second moment of area, bending stress, distance from neutral axis, modulus of elasticity, radius of curvature about the neutral axis. Second moment of area parameters: neutral axis, X and Y axes, distance from neutral axis, second moment of area, section modulus. Evidence requirements Written and oral or graphical evidence which satisfies the PCs as applied to one beam and one cantilever problem with the following restrictions: point loads and uniformly distributed loads only two sections selected from the following: simple rectangular; circular; channel and I sections only. Mechanical Engineering: Unit Specification Strength of Materials (H) 26

28 National Unit Specification: statement of standards (cont) UNIT Strength of Materials (Higher) OUTCOME 3 Apply the simple torsion equation to shafts of circular cross-section. Performance criteria (a) Each parameter, term and relationship of the simple torsion equation is identified consistently with established theory. (b) Parameters associated with polar second moment of area are correctly determined from charts and calculations. (c) Shafts loaded by torque alone are analysed correctly in applying the simple torsion equation. (d) Problems related to application of the simple torsion equation are solved correctly. Note on range for the outcome Parameters: torque, polar second moment of area, torsional stress, radius corresponding to torsional stress, modulus of rigidity, angle of twist, length of shaft. Polar second moment of area parameters: polar axis, radius of gyration, polar second moment of area. Applications: input torque, output torque. Components: circular solid shaft, circular hollow shaft. Evidence requirements Written and/or oral evidence which satisfies the PCs across the range as they apply to one example of loaded shafts for PCs (a), (c) and (d), which can be either circular solid or hollow, both circular solid and hollow shafts for PC (b): loading by torque alone. OUTCOME 4 Design simple components to a given specification. Performance criteria (a) Materials with appropriate engineering properties are selected from an extensive database to meet the requirements of a given application. (b) Design stress values are logically deduced in accordance with established procedures. (c) Loading conditions on common components are analysed correctly. (d) Safe component dimensions to support applied load are determined accurately in terms of the application. Note on range for the outcome Engineering properties: elastic limit stress, proof stress, moduli of elasticity and rigidity, ultimate strength. Materials: low carbon steel, cast iron, aluminium, brass, concrete, polymers. Loading conditions: direct and bending combinations, bending and torsional combinations, temperature stress in complete and partial restraint situations with direct stress combinations. Evidence requirements Written and/or oral evidence which satisfies the PCs and items in the range as they apply to 2 different loading conditions as applied to 2 separate components. The complete requirement should be worked through from material selection, design stress decisions, environmental factors, to the safe loading criteria on critical component sections. Mechanical Engineering: Unit Specification Strength of Materials (H) 27