المواد ميكانيكا

Mechanics of Materials

Strength of Materials

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Course IDCourse NameHoursCourse Type

803323Mechanics of Materials 3, 0, 3Required Core Course

InstructorOfficeExtensionEmail

Mohammed A AlsabbanG1153, Building G1142masabban@uqu.edu.sa

Office HoursMonday11:00am-12:00 noon

Grading الدرجات توزيعHW 10% الواجباتAttendance 10% الحضور1st MT 15% شعبان 27يوم 2nd MT 15% رمضان 19يوم Final 50% شوال 17يوم

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تقديم Introduction

• Mechanics of Materials is the study of the internal effect of external forces applied to structural member. Stress, strain, deformation deflection, torsion, flexure, shear diagram, and moment diagram, topics covered by this subject. تأثير دراسةواالنفعال االجهاد داخليا، المادة على الخارجية القوىالقص واالنثناء، االلتواء الحجم، وتغير والتشوه

بيانيا وابرازهم والعزوم• Materials المتوفرة المواد دراسة• Stiffness (deformation characteristics) المادة مقاومة

الخارجية القوى تأثير تحت والشكل الحجم لتغير• Stability (of load-carrying members) األعضاء اتزان

المواد خصائص Characteristics ofدراسةMaterials

• Laboratory معامل في تتم• Specimens قياسية عينات بأخذ• Test قياسية اختبارات واجراء

• Behaviorورصد

• Physical Characteristics الخصائص وتحديدالميكانيكية

Method of Sectionsالمقاطع طريقة

• Internal resistance of a body داخلية مقاومة• Forces within to balance external forces توازن داخلية قوى

الخارجية القوى• Stable body at rest is in equilibrium جسم الساكن الجسممستقر

• Arbitrary section (suggested where?) اختياري مقطع• Body divided into parts أجزاء الى الجسم يقطع• Parts must also be in equilibrium في المقطوعة االجزاء

اتزان حالة• External forces are balanced by the internal forces القوى

الخارجية القوى مع تتوازن الداخلية• Free Body Diagram (FBD) تحليله في يساعد للنظام حر رسم

Stressاإلجهاد • Stress : Intensity of Force, or force divided by area

[N/m2], called [Pascal] مساحة وحدة على القوة شدة االجهاد

• Perpendicular and Parallel resolution of stress للسطح موازي أو عمودي

) عمودي ) رأسي Normalاجهاد

Stress σ

Normal Stress σ• Tension force produces tensile stresses to lengthen the

member. العضو من ويطيل شد اجهاد عنها ينتج الشد قوة• Compressive force produces compressive stresses to

shorten the member. ضغط اجهاد عنها ينتج الضغط قوةالعضو طول من ينقص

القص Shear Stress τاجهاد• Parallel to plane للسطح موازي

The most general state of stress acting on an element

Equilibriumاالتزان • If the body as a whole is in equilibrium, any

part of it must also be in equilibrium. الجسممتزن منه مقطوع جزء أي المتزن

• ∑ F external = ∑ F internal

• تساوي الخارجية القوى مجموعالداخلية القوى مجموع

Units (SI)Strength of Materials

Lec. 1

• Force [ Newton, N]

•Area [m2 or mm2]

•Stress [Pascal, Pa]

•Pa = Pascal =

15

• MPa = Mega Pascal =

The most general state of stress acting on an element

Axial Load and Normal Stress

• Stress is maximum when plane of cut is perpendicular to force.

• Axial loads produces uniaxial stress• Loads acting through the centeroid of the

cross-sectional area produces uniformly distributed stress

Average Shearing Stress

• Stresses in the plane parallel to the applied force

• Assuming uniformly distributed stress• The average shearing stress is

Critical Section

• Section that have the minimum cross-sectional area and the greatest axial force

• Maximum Stress occurs at the critical section

Equilibrium Equations

• For 2-D (x-y plane) it is reduced to:

Determinate VS Indeterminate

• Depending on the number of the unknown reactions a problem may be identified as:

DeterminateOr

Indeterminate• Ways to solve problems will differ accordingly

Factor of Safety• For design purposes ultimate strength can NOT be

applied directly and a factor of safety is introduced.

Reasons:• Not sure about magnitude of applied force• Assumed Uniformity of material is no exactly true.• Corrosion• Plastic deformation under sustained loads• Cyclic Loading and Fatigue• Residual Stresses

Review

Support Reactions

ReviewEquilibrium:

Internal Resultant Loadings

Review

Coplanar Loadings

Review

Examples

Homework Problems

Review

Average normal stress

Review

Average shear stress

Pure Shear

Homework Problems

Review

Allowable Stress

Review

Design of Simple Connections

Homework Problems