BASIC VOCATIONAL STRENGTH Stress Description first Newton law is about action and reaction. If a cube on the floor, cube will give action toward the floor, and on the contrary, the floor will give the same reaction, so the object are equilibrium condition. Action force (F) and reaction force (F’) from bottom will work toward each the cube section. If we take section A-A from the cube, Center force (F) that direction goes down, and under section, reaction force work toward to the top. On the section surface, molecules on the top and bottom of section surface A_A press each other, so each section large unit gets load : F/A Teknologi dan Rekayasa MAINTENANCE

BASIC VOCATIONAL STRENGTH Load that is received by object molecules of each section area unit is called Stress. Stress is usually stated with Greece letter σ (thau). Teknologi dan Rekayasa MAINTENANCE

BASIC VOCATIONAL STRENGTH KINDS Of STRESS Stress created because of pressure, pulling, bending and reaction. On pulling loading, there happens pulling stress, on the pressure stress, there happens pressure stress. It happen to other loadings Teknologi dan Rekayasa MAINTENANCE

BASIC VOCATIONAL STRENGTH NORMAL STRESS Normal stress happens because of reaction given toward object. If inside force is measured in N, mean while section area in, so stress unit Is : Teknologi dan Rekayasa MAINTENANCE

BASIC VOCATIONAL STRENGTH Normal Stress is If section area = A m2 and Force value Fn = kg. f tangential Stress: Teknologi dan Rekayasa MAINTENANCE

BASIC VOCATIONAL STRENGTH b. Pull Stress Pull stress usually happens to chain, rope, rivet, etc. Chain that is given load W will get pull stress that value depends on the weight Teknologi dan Rekayasa MAINTENANCE

BASIC VOCATIONAL STRENGTH Equality Of Pull stress description : Notes : F = Pull stress A = Section Area Teknologi dan Rekayasa MAINTENANCE

BASIC VOCATIONAL STRENGTH C) Pressure Stress Pressure stress happens if a rod ls given force F on the contrary side and laid on one force line, for example its happen to beam of building that haven’t bended yet, bicycle arm, connecting rod. Pressure stress can be written : Teknologi dan Rekayasa MAINTENANCE

BASIC VOCATIONAL STRENGTH Teknologi dan Rekayasa MAINTENANCE

BASIC VOCATIONAL STRENGTH d) Move Stress Move Stress happens if an object work with two force in contrary direction, perpendicular rod axis, force in the same line, but on the section doesn’t happen moment. This stress usually happens to construction such as rivet, scissor, and bolt joint Teknologi dan Rekayasa MAINTENANCE

BASIC VOCATIONAL STRENGTH On the picture above, two force with same value in contrary direction. Force F work spread on section A. On the material will appear move stress. The value is For construction on rivet, so F maximum is Teknologi dan Rekayasa MAINTENANCE

BASIC VOCATIONAL STRENGTH Move stress happen because of radial force that works on normal section with relative small space, so bending of object is ignored. For this case, the stress that happens is Teknologi dan Rekayasa MAINTENANCE

BASIC VOCATIONAL STRENGTH If on Construction has amount of rivet, so according to the equality below, the move stress is D = diameter of rivet Teknologi dan Rekayasa MAINTENANCE

BASIC VOCATIONAL STRENGTH e) Bending Stress For example on machines shaft and wheel shaft in pillar condition. So It’s tangential stress Teknologi dan Rekayasa MAINTENANCE

BASIC VOCATIONAL STRENGTH Mb = bending moment Wb = bend resistant moment Teknologi dan Rekayasa MAINTENANCE

BASIC VOCATIONAL STRENGTH f) Twist stress Twist stress often happen to gear shaft and torque rods of car, drilling process. So it’s tangential stress Teknologi dan Rekayasa MAINTENANCE

BASIC VOCATIONAL STRENGTH An object that get twist load will create twist stress : Mt = torque Wp = polar resistant moment back Teknologi dan Rekayasa MAINTENANCE