By the end of this chapter, you will be able to:
Mastering these skills will help you build strong, reliable mechanical systems that perform safely and efficiently in real-world engineering work.
Torsion plays a critical role in welding engineering, especially when assessing the strength and durability of welded joints subjected to twisting forces. Understanding torsion theory equips welding professionals with the ability to analyze and design components that resist failure under torque, which is essential in structural frameworks, machinery shafts, and piping systems common in Kenya’s manufacturing and construction sectors. This chapter delves into the fundamentals of torsion and the methods of torque analysis, providing welding technicians with the technical foundation to ensure safety and reliability in their work.
Torsion is a mechanical phenomenon that occurs when a structural element is subjected to a twisting force, causing shear stresses within the material. In welding, components like shafts, rods, and tubular structures often experience torsion, making it essential to understand how these forces interact with welded joints. Proper analysis of torsion helps welding professionals prevent catastrophic failures in equipment used in industries such as agro-processing, automotive repair, and infrastructure development.
Torsion is the twisting of an object due to an applied torque or moment. It involves the rotation of one end of a shaft or structural member relative to the other, resulting in internal shear stresses distributed over the cross section. In mechanical systems, torsion is common in drive shafts, axles, and welded pipe joints where rotational power is transmitted. For welding professionals, recognizing torsion helps in selecting suitable welding techniques and inspection methods to maintain structural integrity.
When a shaft or member is twisted, it experiences shear stress, which is the force per unit area acting parallel to the cross section. This shear stress varies linearly from zero at the axis of the shaft to a maximum at the outer surface. Correspondingly, shear strain measures the deformation angle due to this stress. Understanding these parameters helps welders evaluate how much twisting a welded joint can withstand before failure, guiding decisions on weld size and type.
Different materials respond uniquely to torsional loads. Ductile materials, such as mild steel commonly welded in Kenya’s fabrication shops, undergo significant plastic deformation before failure, allowing visible warning signs like twisting or elongation. Conversely, brittle materials like cast iron fail suddenly under torsion without much deformation. Welding professionals must consider the material properties when designing and inspecting welds for torsional applications to avoid premature failure.
The shape of a component’s cross section greatly influences its torsional strength. Circular shafts distribute shear stress uniformly, making them ideal for torsional loading. Non-circular sections, such as rectangular or I-beams, experience stress concentrations and warping under torsion. Welders working on structural frames or machine components must understand these effects to apply appropriate welding procedures and reinforcements, ensuring the joint’s ability to resist twisting forces.
Create a free account to open more of this chapter.
Free: practical guides, quick cards, workplace scenarios and more.
Create a free accountThis chapter introduced the concept of torsion as the twisting of an object due to an applied torque, emphasizing its significance in mechanical systems. It then explored torque analysis, detailing how forces cause rotational effects that must be quantified for design and safety. The analysis of shafts was examined in depth, distinguishing between shafts arranged in series and those arranged in parallel, each configuration affecting torque distribution differently. The chapter further addressed the calculation of the angle of twist, which measures the deformation experienced by a shaft under torsion. Finally, engineers' torsion equations were presented as essential tools for determining shear stress and angle of twist in shafts, enabling precise mechanical design and assessment. Together, these topics provide a comprehensive framework for understanding and analyzing torsional effects in mechanical components.
Type: Individual
| Tools & Equipment | Materials |
|---|---|
| Torsion testing rig with handle | Mild steel round shaft Ø25 mm x 300 mm |
| Vernier caliper | |
| Steel rule | |
| Try square | |
| Safety boots | |
| Leather gloves | |
| Overall |
| S/N | Item | Quantity |
|---|---|---|
| 1 | Mild steel round shaft Ø25 mm x 300 mm | 1 Pc per Candidate |
| 2 | Torsion testing rig with handle | 1 Set per 3 Candidates |
| 3 | Vernier caliper | 1 Pc per Candidate |
| 4 | Steel rule | 1 Pc per Candidate |
| 5 | Try square | 1 Pc per Candidate |
| 6 | Safety boots | 1 Pair per Candidate |
| 7 | Leather gloves | 1 Pair per Candidate |
| 8 | Overall | 1 Pc per Candidate |
| Items to be Evaluated | Marks Available | Marks Obtained | Comments |
|---|---|---|---|
| TASK 1: Safety and Personal Protective Equipment | |||
| Wore overall correctly (Award 1 or 0 marks) | 1 | ||
| Wore safety boots (Award 1 or 0 marks) | 1 | ||
| Wore leather gloves (Award 1 or 0 marks) | 1 | ||
| Sub-Total | 3 | ||
| TASK 2: Setup and Demonstration of Torsion | |||
| Measured and verified shaft diameter and length using vernier caliper and steel rule (Award 2 or 0 marks) | 2 | ||
| Secured the mild steel shaft properly in the torsion testing rig (Award 2 or 0 marks) | 2 | ||
| Applied twisting force gradually using the torsion rig handle (Award 2 or 0 marks) | 2 | ||
| Observed and explained the physical effect of torsion (twisting and shear stress) (Award 3 or 0 marks) | 3 | ||
| Sub-Total | 9 | ||
| TASK 3: Housekeeping | |||
| Cleaned the work station after demonstration (Award 1 or 0 marks) | 1 | ||
| Disposed of any waste materials correctly (Award 1 or 0 marks) | 1 | ||
| Returned tools and equipment to their proper places (Award 1 or 0 marks) | 1 | ||
| Sub-Total | 3 | ||
| PRODUCT CHECKLIST | |||
| Shaft dimension verification: diameter Ø25 mm ±1 mm and length 300 mm ±1 mm (Award 3 or 0 marks) | 3 | ||
| Proper securing of shaft in the torsion rig without slippage (Award 2 or 0 marks) | 2 | ||
| Clear and accurate explanation of torsion concept including twisting effect and shear stress (Award 4 or 0 marks) | 4 | ||
| Sub-Total | 9 | ||
| GRAND TOTAL | 24 | ||
Type: Individual
| Tools & Equipment | Materials |
|---|---|
| Dial gauge with stand | Mild steel shaft diameter 40 mm, length 600 mm |
| Vernier caliper 0-150 mm | |
| Torque wrench (0-100 Nm range) | |
| Protractor |
| S/N | Item | Quantity |
|---|---|---|
| 1 | Mild steel shaft diameter 40 mm, length 600 mm | 1 Pc per Candidate |
| 2 | Dial gauge with stand | 1 Pc per Candidate |
| 3 | Vernier caliper 0-150 mm | 1 Pc per Candidate |
| 4 | Torque wrench (0-100 Nm range) | 1 Pc per Candidate |
| 5 | Protractor | 1 Pc per Candidate |
| 6 | Safety boots | 1 Pair per Candidate |
| 7 | Leather gloves | 1 Pair per Candidate |
| 8 | Overall/dustcoat | 1 per Candidate |
| Items to be Evaluated | Marks Available | Marks Obtained | Comments |
|---|---|---|---|
| TASK 1: Safety and Preparation | |||
| Wore all prescribed PPE correctly (safety boots, gloves, overall) (Award 1 mark for each PPE worn correctly, else 0) | 3 | ||
| Selected and prepared tools and materials for torque analysis (Award 2 marks for correct selection and preparation, else 0) | 2 | ||
| Sub-Total | 5 | ||
| TASK 2: Measurement and Data Collection | |||
| Measured shaft diameter accurately using vernier caliper (Award 2 marks for measurement within ±0.1 mm, else 0) | 2 | ||
| Mounted dial gauge correctly to measure angular displacement (Award 3 marks for proper setup and zeroing, else 0) | 3 | ||
| Applied torque using torque wrench gradually and recorded angular displacement (Award 5 marks for correct application and accurate reading, else 0) | 5 | ||
| Sub-Total | 10 | ||
| TASK 3: Calculation and Analysis | |||
| Calculated torque using T = GJθ/L with correct values and units (Award 5 marks for correct formula application and unit consistency, else 0) | 5 | ||
| Interpreted results to assess shaft safety and performance (Award 3 marks for logical conclusions based on calculations, else 0) | 3 | ||
| Sub-Total | 8 | ||
| TASK 4: Housekeeping | |||
| Cleaned work area and returned tools and materials to designated places (Award 1 mark each for cleaning, waste disposal, and tool return, else 0) | 3 | ||
| Sub-Total | 3 | ||
| PRODUCT CHECKLIST | |||
| Accurate measurement of shaft diameter 40 mm ± 0.1 mm (Award 3 marks for measurement within tolerance, else 0) | 3 | ||
| Correct angular displacement recorded with dial gauge (±1 degree tolerance) (Award 3 marks for correct and consistent readings, else 0) | 3 | ||
| Torque calculated correctly for shaft length 600 mm and diameter 40 mm (Award 6 marks for correct application of torsion formula and units, else 0) | 6 | ||
| Sub-Total | 12 | ||
| GRAND TOTAL | 38 | ||
At the start of this chapter we promised you would be able to:
Tick each one you can genuinely do.
So, are you there yet?
You're competent when you can confidently do 50% or more of what this chapter promised.
Sign in to record how you're doing.