# Design of Screw Jack Numerical 1 Part 2 - Design Against Static Loads - Machine Design I | Summary and Q&A

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April 3, 2022
by
Ekeeda
Design of Screw Jack Numerical 1 Part 2 - Design Against Static Loads - Machine Design I

## TL;DR

This video discusses the analysis of the design parameters of a screw jack and determines whether they are safe or not.

## Key Insights

• 🎃 The design parameters of a screw jack are analyzed to determine if they are safe.
• 🧑‍🏭 The total torque acting on the screw is calculated by considering the load and friction.
• 🎃 The compressive stress and shear stress in the screw jack are calculated using standard formulas.
• ❓ The maximum principal stress and maximum shear stress are determined and compared to the allowable values.
• 🧑‍🏭 Material selection for the screw is based on the factor of safety and the allowable stress.
• 🥥 The induced shear stress in the nut is calculated and compared to the allowable value.
• 🍉 The nut and screw are found to be safe in terms of shear and combined stresses.

### Q: How is the total torque in a screw jack calculated?

The total torque is calculated by adding the torque from the load and the torque from the friction. The formulas for these torques are provided in the video.

### Q: What are the values of the compressive stress and shear stress in the screw jack?

The compressive stress is calculated to be 32.37 N/mm², and the shear stress is calculated to be 33.14 N/mm².

### Q: How are the maximum principal stress and maximum shear stress determined?

The maximum principal stress is calculated using the formula involving compressive stress and shear stress. The maximum shear stress is calculated using an empirical relation. The values obtained are 52.934 N/mm² and 36.34 N/mm², respectively.

### Q: How is the material selection for the screw determined based on the factor of safety?

The allowable stress is divided by the factor of safety to obtain the maximum stress that can be allowed. Based on this value, a material with a yield strength of approximately 210 N/mm² can be selected.

## Summary & Key Takeaways

• The video analyzes the combined stresses acting on the screw jack and calculates the total torque.

• The compressive stress and shear stress are determined using standard formulas.

• The maximum principal stress and maximum shear stress are calculated and compared to the allowable values.