SOLUTION(a) The weight of the bicyc

SOLUTION
(a) The weight of the bicycle frame made from steel is stated to be 30 pounds. The volume of this frame will be
V frame = (30 X 454 g/lb)/(7.8) = 1746 cm3
For aluminum frame the weight will be
Wal = (1746 cm3) X (2.7 g/cm3) X (1 lb/454) grams = 10.38 lbs
Another and simpler way to arrive at this answer is to take the ratio of densities, since the volume is assumed constant.
The weight of the aluminum alloy frame
Walloy = (density of aluminum alloy/density of steel)
X (wt. of the steel frame)
= (2.7/7.8) X 30 lb = 10.38 lb
Thus, the aluminum frame weighs roughly one-third of the steel frame. Similarly, the weight of titanium frame will be
WTi = (density of titanium alloy/density of steel)
X (wt. of the steel frame)
= (4.5/7.8) X 30 lb = 17.3 lb
Finally, the weight of the frame made using carbon-fiber composite will be
Wcf = (density of carbon fiber composite/density of steel)
X (wt. of the steel frame)
= (1.85/7.8) X 30 lb = 7.1 lb
As can be seen, substantial reduction in weight is possible using materials other than steel.
(b) One of the other factors that comes into play is the stiffness of the structure. This is related to the elastic modulus of the material (Chapter 2). For ex- ample, for the same tube dimensions, an aluminum tube will be not as stiff as steel. This will make the aluminum frame bicycle ride “soft.” This effect can be compensated for by making the aluminum tubes larger in diameter and the walls of the tubes thicker. Some other factors to consider are the toughness of each of the materials. For example, even though a carbon- fiber frame is very light, it is relatively brittle. Additional considerations would be the ability to weld or join the frame to other parts of the bicycle, corrosion resistance, and of course, cost.
EXAMPLE 1-2
Ceramic-Carbon-Fiber Brakes for Cars
Car breaks are typically made using cast iron and weigh about 20 pounds. What other materials can be used to make brakes that would last long and weigh less?
SOLUTION
The brakes could be made using other lower density materials, such as alumi- num or titanium. Cost and wear resistance are clearly important. Titanium alloys will be very expensive, and both titanium and aluminum will wear out more easily.
We could make the brakes out of ceramics, such as alumina (Al2O3) or silicon carbide (SiC), since both have densities lower than cast iron. However, ceramics are too brittle, and even though they have very good resistance, they will fracture easily.
We can use a material that is a composite of carbon fibers and ceramics, such as SiC. This composite material will provide the lightweight and wear- resistance necessary, so that the brakes do not have to be replaced often. Some companies are already producing such ceramic-carbon-fiber brakes.

Kết quả (Hmong) 1:

TOV(a) tus luj ntawm lub tsheb kauj vab kablus ua los ntawm cov hlau no teev kom muaj 30 phaus. Qhov ntim ntawm no thiab yuavV hom = (30 X 454 g/lb)/(7.8) = 1746 cm3Rau txhuas qhov nyhav thiab yuavTeb = (1746 cm3) X (2.7 g/cm3) X (1 lb/454) grams = 10.38 lbsLwm thiab yooj yim rau hnub uas yuav tuaj teb lus no yog muab piv rau ntawm yam, vim lub ntim no assumed qhov.Tus luj ntawm lub txhuas alloy numWalloy = (ntom ntawm txhuas alloy/ceev cov hlau)X (wt. ntawm tus ncej steel)= (2.7/7.8) x 30 lb = 10.38 lbYog li, cov txhuas num nyhav roughly ib feem peb ntawm cov kablus steel. Mob(nurses), cov luj ntawm titanium thiab yuavWTi = (ntom ntawm titanium alloy/ceev cov hlau)X (wt. ntawm tus ncej steel)= (4.5/7.8) x 30 lb = 17.3 lbThaum kawg, tus luj ntawm cov kablus ua siv cov-fiber ntau composite yuavWcf = (ntom ntawm carbon fiber composite/ceev cov hlau)X (wt. ntawm tus ncej steel)= (1.85/7.8) x 30 lb = 7.1 lbRaws li tau pom, kev txo nyob cus puas yuav tau siv cov ntaub ntawv uas tsis yog hlau.(b) yog ib tus lwm yam ua tawm mus ua si yog tus mob heev los ntawm cov qauv. Qhov no muaj feem xyuam rau lub elastic modulus ntawm cov khoom siv (Tshooj 2). Rau ex-xam, rau tib qhov raj ntev, ib lub raj txhuas yuav tsis kom nruj li hlau. Qhov no yuav ua kom txhuas thiab luv thij caij "mos." Cov nyhuv no yuav raug rau compensated los ntawm kev txiav txoj txhuas menyuam loj hauv txoj kab uas hla thiab lub phab ntsa rau lub thicker leeg. Tej lwm yam yuav tau xav txog yog qhov toughness txog txhua yam ntawm cov ntaub ntawv. Piv txwv li, txawm tias muaj fiber ntau cov ncej yog pom pom, nws yog kuj nkig. Xav txog kev teem ntxiv yuav muaj peev xwm weld los yog koom cov num lwm qhov ntawm lub tsheb kauj vab, kuj corrosion, thiab tiv thaiv, kim. PIV TXWV LI 1-2Ceramic-Carbon-Fiber Brakes rau tshebTsheb so no feem ntau yog ua los siv hlau cam khwb cia thiab luv li 20 phaus. Lwm yam khoom siv ua brakes uas yuav kav ntev thiab luv luv dua?TOVTus brakes yuav ua siv rau lwm sab ceev cov ntaub ntawv, xws li alumi-num los yog titanium. Nqi thiab coj kuj yog ib qho tseem ceeb kom meej meej. Titanium alloys yuav kim heev, thiab titanium thiab txhuas yuav hnav kom paub ntxiv tau yooj yim.Peb yuav ua tus brakes tawm hauv ceramics, xws li alumina (Al2O3) los yog silicon carbide (SiC), vim yam tsawg dua hlau cam khwb cia muaj ob yam tib si. Tiam sis, ceramics nkig heev, thiab txawm tias lawv tau kuj zoo heev, lawv yuav fracture tau yooj yim.Peb yuav siv ib cov khoom uas yog ib tug composite carbon fibers thiab ceramics, xws li SiC. Qhov khoom ntawd puas yuav muab cov khaub-ncaws nyias thiab coj-ua hauj tsim nyog, kom tus brakes tsis tas yuav muab hloov kom ntau. Tej tuam txhab uas muag cov twb yuav ua tau tej tus brakes ceramic-cov-fiber ntau.

Kết quả (Hmong) 2:

Kua
(a) Lub ceeb thawj ntawm lub tsheb kauj vab ncej ua los ntawm steel yog hais yuav 30 phaus. Lub volume ntawm no thiab yuav tau
V ncej = (30 X 454 g / lb) / (7,8) = 1746 cm3
Rau txhuas ncej lub qhov ceeb thawj yuav tsum
Wal = (1746 cm3) X (2.7 g / cm3) X (1 lb / 454) grams = 10,38 lbs
Lwm thiab yooj yim txoj kev uas yuav mus txog rau ntawm cov lus teb no yog coj tus piv ntawm densities, txij li thaum lub volume yog assumed qhov.
Tus luj ntawm lub txhuas hlau ncej
Walloy = (kev ceev ntawm txhuas hlau / ceev ntawm steel)
X (wt. ntawm cov hlau ncej)
= (2.7 / 7.8) X 30 lb = 10,38 lb
Yog li, lub txhuas ncej nyhav roughly ib feem peb ntawm cov hlau ncej. Ib yam li ntawd, tus luj ntawm titanium thiab yuav tsum
WTi = (kev ceev ntawm titanium hlau / ceev ntawm steel)
X (wt. Ntawm cov hlau ncej)
= (4.5 / 7.8) X 30 lb = 17,3 lb
Thaum kawg, tus luj ntawm lub ncej ua siv cov pa roj carbon-fiber puas yuav
WCF = (kev ceev ntawm cov pa roj carbon fiber puas / ceev ntawm steel)
X (wt. ntawm cov hlau ncej)
= (1.85 / 7.8) X 30 lb = 7.1 lb
Raws li yuav pom, ntau yam pauv loj yuav txo tau nyob rau hauv hnyav yog tau siv cov ntaub lwm yam tshaj li hlau.
(b) Ib tug ntawm cov yam uas los mus ua si yog tus nruj ntawm cov qauv. Qhov no yog hais txog kev mus rau lub ywj modulus ntawm cov khoom (Tshooj 2). Rau lo xam, rau tib lub raj qhov ntev, ib tug txhuas raj yuav tsum tsis raws li txhav li hlau. Qhov no yuav ua rau lub txhuas ncej tsheb kauj vab caij "mos mos." Qhov no ua rau yuav compensated rau los ntawm kev ua lub txhuas hlab loj nyob rau hauv lub cheeb thiab cov phab ntsa hauv lub hlab thicker. Ib txhia lwm yam tseem ceeb los xav txog yog cov toughness ntawm txhua tus ntawm cov ntaub ntawv. Piv txwv li, txawm tias ib tug carbon- fiber ncej yog heev lub teeb, nws yog tus nkig. Ntxiv xav txog kev teem yuav cov muaj peev xwm mus weld los yog koom nrog tus ncej rau lwm qhov chaw ntawm lub tsheb kauj vab, corrosion kuj, thiab ntawm cov hoob kawm, tus nqi.
QAUV 1-2
hub-Pa Roj Carbon-Fiber Brakes rau Tsheb
Tsheb so yog feem ntau tau ​​siv cam khwb cia hlau thiab luj txog 20 phaus. Yuav ua li cas lwm cov ntaub ntawv yuav siv tau los ua brakes uas yuav kav ntev thiab luj tsawg?
Kua
Lub brakes yuav tau muab siv rau lwm yam sab ceev cov ntaub ntawv, xws li alumi- num los yog titanium. Nqi thiab coj kuj yog kom meej meej ib qho tseem ceeb. Titanium alloys yuav yuav kim heev, thiab ob titanium thiab txhuas yuav hnav tawm tau yooj yim dua.
Peb yuav ua tus nres tawm ntawm ceramics, xws li alumina (Al2O3) los yog pob zeb ntais carbide (sic), txij thaum ob leeg muaj densities qis tshaj cam khwb cia hlau. Txawm li cas los, ceramics yog ib yam nkaus thiab nkig, thiab txawm tias lawv muaj zoo heev kuj, lawv yuav tawg yooj yim.
Peb yuav siv ib cov khoom uas yog ib tug puas ntawm cov pa roj carbon fibers thiab ceramics, xws li sic. Qhov no puas cov ntaub ntawv uas yuav muab cov khaub-ncaws nyias thiab wear- kuj tsim nyog, yog li ntawd tus brakes tsis muaj yuav tsum tau hloov ntau. Ib txhia tuam txhab uas muag twb ua xws tej hub-carbon fiber ntau cov brakes.